Salivary Interactions With Chemosensations

This study is designed to test the relationship between salivary proteins, flavor sensation, and flavor exposure. For this study, we will test the bitterness/astringency of epigallocatechin gallate (EGCG, a polyphenol), the oleogustus (fatty acid taste) of linolenic acid, and the spiciness of capsaicin in conjunction with the concentration of specific salivary proteins (initially: salivary proline rich proteins for EGCG intervention, lipocalin-1 for the other two, but other proteins may be identified in the post-hoc analysis of the salivary proteome). We will test whether higher expression of these specific salivary proteins correlates with lower intensity of these flavors. We will further attempt to confirm the role of these salivary proteins using food-sourced functional analogs for these proteins. We would expect the food-sourced protein to have the same effect on flavor as the salivary protein if our hypotheses about salivary proteins' influence on flavor are correct. Finally, we will also use denatured versions of the food-sourced proteins to again confirm that effects are due to the function of these proteins binding the flavor.

Additionally, we will repeatedly expose individuals to the flavors by having them rinse and swallow solutions of the flavor compounds multiple times per day for two weeks. We will then re-evaluate the sensory ratings and salivary protein profiles. Two weeks of rinsing and swallowing a control solution will be used as a control during this intervention (for each of the flavors of interest).

To collect saliva and establish bitterness/astringency perception, we will use an acute tasting protocol. Participants will rinse with water, then taste and swallow, then taste and expectorate a solution of the flavor of interest. Saliva will be frozen for later proteomic analysis. Next participants will taste solutions of: flavor, flavor with food analog, the flavor with denatured food analog, water, water with the food analog, and water with denatured food analog. The participants will rank these solutions in order from least intense to most intense for the flavor quality of interest (bitterness/astringency for EGCG). After this, participants will taste all 6 samples again, and rate each individually for the intensity of the bitterness/astringency. After a short wait, this tasting and intensity rating will be repeated. All tastings will be done in counterbalanced order, and solutions will be labeled with randomized 3-digit codes.

This acute tasting protocol will be done: at baseline, after 2 weeks on one intervention (repeated tasting of flavor or control), after 2 weeks on the other intervention.